1. Field of the invention
The invention relates to a sintered, dry-running friction lining with no binding agent, with a friction lining body comprising a metallic matrix, at least one abrasive material and at least one filler, a dry-running friction component with a base part to which a friction lining is joined, as well as a friction unit with at least one dry-running friction component.
2. Prior Art
Organically resin-bonded friction linings are used in conventional dry-running transmission systems of automotive vehicles.
Patent specification DE 29 24 540 A, for example, describes a product for producing components with a metallic composition, made up of at least a fine steel fiber powder with a loose density of between 0.2 and 1.5 g/cm3, the carbon content of which is between 0.95 und 1.10% by weight, and the chromium content of which is between 1.3 and 1.6% by weight, which is heat treated so that the microscopic structure, as viewed from an inspection plane intersecting a metal particle, exhibits a fine distribution of spherical iron and chromium carbide based on the formula (FeCr)3C in a mixed base mass of high-strength martensite and deformable austenite. This fibrous powder is used for a friction lining for brakes in a proportion of 30 to 85% by weight and this friction lining additionally contains mineral and organic fillers of a type and in amounts which satisfy the operating properties required of the lining. It is used in particular to produce friction linings for clutches or brakes. The friction linings contain between 10 and 20% of polymerisable phenol binders.
These materials are distinctive due to a low tendency to friction-induced vibrations (e.g. clutch engagement) but can be used only at very low temperatures and energy loads, mainly due to the raw materials used for the matrix, in other words the resin.
Modern drive trains are becoming increasingly lightweight but must be capable of transmitting higher powers whilst improving driving comfort and fuel efficiency at the same time. Due to the need to keep the vehicle weight as low as possible, the size of clutches is very severely limited. This in turn has a major effect on the stresses of the friction lining because less mounting space for the clutch means smaller lining surfaces, resulting in higher energy and temperature loads on the friction material.
The metallic friction linings available these days, however, are all capable of withstanding very high energy and thermal loads, have high coefficients of friction and low abrasion, but do have a very strong tendency to friction vibration which can spread through the entire drive train and thus have a very negative effect on the driving comfort of the vehicle.
Other friction components are described in the prior art, in which the friction lining is made from sintered materials. For example, patent specification DE 44 43 666 A describes a component, in particular a synchronizer ring, with friction surfaces for synchronizing friction in automotive gear systems. Here too, this invention is driven by the move towards increasing miniaturization and ever more demanding requirements in terms of power transmission and shifting comfort. The material used for the friction surfaces of the component in this DE-A is a sintered bronze which is superficially largely free of pores and contains metallic and non-metallic additives to improve friction behavior, wear resistance and shifting comfort in the form of up to 6% by weight zinc, up to 6% by weight of nickel, up to 3% by weight of molybdenum, 1 to 6% by weight of SiO2 and/or Al2O3, optionally 0.2 to 6% by weight of graphite and/or molybdenum disulphide, the rest being bronze of a defined particle size in the initial powder. This sintered bronze is intended for oil-lubricated parts for synchronizing friction in automotive gear systems.
Patent specification DE 42 39 441 A, on the other hand, addresses the problem of producing friction materials of a reduced density, in particular friction linings of dry clutches, and proposes subjecting a blank containing the components of the friction materials to a pressing process and optionally a first thermal finishing treatment and/or a final thermal treatment, and one or more reagents are added to the blank prior to the pressing process, which lead to a reduction in the density of the end product due to the fact that they escape by forming a gas or/and react due to the splitting of gaseous molecules or/and completely decompose into volatile elements during the pressing process, the first thermal finishing treatment or/and the final thermal treatment, and the pressing operation and optionally the first thermal finishing treatment or/and the thermal final treatment are operated in such a way that shrinkage of the blank is prevented as far as possible.
Patent specification DE 42 17 948 C discloses a method of producing porous friction surfaces on friction elements on a synchronizer unit. The friction surface is formed by a sintered body made from sintered grains. The friction surface is ground and, after grinding, treated with a jet of gaseous or liquid medium so that side edges created on the sintered grains constituting the surface of the friction surface during the process of grinding the friction surface are broken away from the sintered grains due to the mechanical action of the jet and fed away from the sintered body. As a result, the accesses to the pore cavities of the sintered friction body are made free again after grinding so that the entire storage capacity of the friction body is made available again without any restrictions. The intention is to allow lubricants to penetrate and be stored in lubricated friction pairings.
Patent specification DE 32 32 865 A discloses a method and a device for producing a friction element for a motor vehicle or motor bicycle disc brake. To this end, a powdered friction material is placed in a mould cavity and compacted. A first and a second resistance electrode are used for this purpose. As a result, the friction material is sintered and joined to a pressure plate closing off one end of the mould cavity. The first electrode has an end surface which can be moved into contact with the pressure plate and has a cut-out provided in it which is partially filled with a graphite insert which has a lower electrical conductivity than the rest of the first electrode. The second electrode may be provided with a similar insert and may come into contact with the friction material either directly or via a sub-electrode made from graphite disposed in between. This results in a good electrical contact between the friction material and the electrode and a uniform current flow through the material. The material used for the friction lining is a powder containing copper, tin, lead and graphite, silicon oxide, aluminum oxide and molybdenum disulphide in various compositions. The proportion of silicon oxide used is 1.0 and 2.8% by weight and that of aluminum oxide between 4.9 and 9.7% by weight. Another option is to use silicon nitride in a proportion of 8.3 percent by weight. This enables friction linings of differing porosities to be produced, the final density of which is in the range of between 72.6% and 90.5%.